Final answer:
To assign the value 'true' to the variable 'teenage' only if the variable 'kidage' is 13, one would use a conditional statement in a programming language, such as an if-else statement or a conditional operator.
Step-by-step explanation:
In the context of programming, when you want to assign the value 'true' to the variable 'teenage' if the value of the variable 'kidage' is 13, you would typically use a conditional statement. In most programming languages, this can be done using an if-else statement or a conditional operator. For example, in Python, the code would be:
teenage = True if kidage == 13 else False
This line checks if kidage is equal to 13, and if it is, it sets teenage to true; otherwise, it sets teenage to false.